Cadmium fixation method for farmland soil and application

The invention provides a farmland soil cadmium fixation method and application. The farmland soil cadmium fixation method comprises the following steps: controlling the farmland soil to contain ferrous ions and nitrite ions; the molar ratio of ferrous ions to cadmium is (500-1000): 1, the molar ratio of nitrite ions to ferrous ions is 1: (1-10), the cadmium fixation requirement is met, the cadmium fixation rate can be stabilized at 88%, and 66.67% of cadmium fixed by iron minerals exists in a combined state; in actual cadmium-polluted soil, the concentration of effective-state Cd in the soil is reduced by 50% due to accumulation of NO2-N, the migration performance of Cd in the soil is reduced, and solidification and stabilization of Cd in farmland soil are achieved. Besides, ferrous ions (Fe < 2 + >) and nitrite ions (NO2-N) involved in the method are components already contained in farmland soil, no allogenic material is newly added, and secondary pollution cannot be caused; meanwhile, the nitrogen fertilize